This invention relates to a method for the production of oil. More particularly this invention pertains to a method of inhibiting asphalt precipitation in the flow path of an oil production well.
Asphalt precipitation may occur during the production of crude oil at any location in the flow path of an oil production well. This flow path extends from the reservoir formation surrounding the inflow zone of the well, via the production tubing or tubings within the well to the production lines near the wellhead. At each location precipitation of asphalt may seriously impede the productivity of the well. Asphalt or asphaltenes are together with wax or paraffin one of the most serious clogging constituents of crude oil. Numerous attempts have been made to restrict precipitation of these clogging constituents by injecting suitable solvents into the flow path of an oil production well.
U.S. Pat. No. 3,574,319 discloses that paraffin deposition in a paraffin-containing oil production well can be prevented by injection of asphaltic crude oil into the well.
U.S. Pat. No. 4,756,368 discloses that cracked oil fractions may be reinjected into a well to maintain a wax-containing crude oil in fluid state. European patent 89,986 discloses that condensed gaseous phases of well effluents may be reinjected into a well to avoid paraffin or asphalt precipitation. U.S. Pat. No. 2,765,850 discloses that dewaxed oil may be reinjected into a production well to reduce wax deposition.
The article, "High-Pour-Point and Asphaltic Crude Oils and Condensates," published by R. N. Tuttle in the Journal of Petroleum Technology of June 1983, discloses that circulation of oil was used as early as 1944 to reduce the asphaltenes problem.
U.S. Pat. No. 4,767,545 mentions that prevention or removal of asphaltenes deposits can be attempted chemically through the use of aromatic solvents, solvent accelerators, or the resinous components of crudes, but that these procedures can be prohibitively expensive and may not be effective.
It is an object of the present invention to provide an efficient method of inhibiting asphalt precipitation in an oil production well which does not require injection of expensive solvents or the utilization of special treatment plants for reinjection of specific fractions of the produced crude oil into the well.